A conventional product code is composed of one type of code in a longitudinal direction and another type of code in a lateral direction (for example, refer to Non-Patent Literature 1 presented in below and FIG. 14 of the present application). This frame configuration is defined as a product code frame. With regard to the product code, although any of coding in the longitudinal direction and the coding in the lateral direction may be performed first, an element code in the lateral direction and the element code in the longitudinal direction are conveniently defined as an outer code C1 (coded first) and an inner code C2 (subsequently coded), respectively. An arrow 901 depicted in FIG. 14 indicates a coding direction of the outer code C1 (from left to right on the paper). In the arrow 901, a section 901a indicates an allocation of an information sequence, and a section 901b indicates an allocation of a parity sequence. A coding to separate an information sequence area 911 and a parity sequence area 912 from each other after the coding is referred to as a systematic coding.
Similarly, an arrow 902 indicates a coding direction of the inner code C2 (from top to bottom on the paper) in which the information sequence and the parity sequence are allocated to a section 902a and a section 902b, respectively. Also in this case, a systematic coding in which the information sequence area 911 and a parity sequence area 913 are separated from each other is employed. Meanwhile, in a case of the product code, a Check-on-Check area 914 to be allocated to the parity sequences 901b and 902b of both of the outer code C1 and the inner code C2 may be provided.